1. Field of the Invention
The present invention relates to the structure of a reclining seat.
2. Description of the Related Art
A vehicle's reclining seat with a seat belt retractor incorporated in the seat backrest is well known in the related art. This conventional reclining seat 100 is shown in FIG. 8.
The reclining seat 100 chiefly comprises a seat backrest 101 and a seat cushion 102.
The seat backrest 101 includes a laterally outer frame 103 disposed to form the laterally outer side of the seat backrest 101, a laterally inner frame 104 disposed to form the laterally inner side of the seat backrest 101, and an upper frame 105 connecting the upper end portion of the laterally outer frame 103 and the upper end portion of the laterally inner frame 104 together.
The laterally outer frame 103 of the seat backrest 101 has a shoulder anchor 107 provided at its upper end portion for supporting a seat belt 106. The seat cushion 102 includes a cushion frame 110. The cushion frame 110 has a lower anchor 108 provided at its laterally outer end portion for fixing the seat belt 106, and further has a buckle 109 provided at its laterally inner end portion for detachably fastening the seat belt 106. The seat belt 106 is drawn back into a retractor (not shown) provided interiorly of the seat backrest 101.
As shown in FIG. 8, a laterally outer locking mechanism 111 pivotally connects the laterally outer frame 103 of the seat backrest 101 with the rear outer end of the cushion frame 110, and is able to lock the laterally outer frame 103 at a desired sloping position with respect to the cushion frame 110.
Likewise, a laterally inner locking mechanism 112 pivotally connects the laterally inner frame 104 of the seat backrest 101 with the rear inner end of the cushion frame 110, and is able to lock the laterally inner frame 104 at the desired sloping position with respect to the cushion frame 110.
The laterally outer locking mechanism 111 is also equipped with a release lever 113, which is operated by a passenger. If the extreme end portion of the release lever 113 is lifted by the passenger, the locked state between the laterally outer frame 103 and the cushion frame 110 by the laterally outer locking mechanism 111 is released, and at the same time, a shaft 114 connecting the laterally outer locking mechanism 111 and laterally inner locking mechanism 112 together is rotated. The rotation of the shaft 114 releases the laterally inner frame 104 and cushion frame 110 locked by the laterally inner locking mechanism 112.
Conversely, if the lifted release lever 113 is lowered to its original position, the laterally outer frame 103 and cushion frame 110 are relocked and the laterally inner frame 104 and cushion frame 110 are relocked.
Note that the reclining seat 100 is constructed such that if relative rotation occurs between the laterally outer and inner locking mechanisms 111, 112 and the shaft 114, the locked state between the seat backrest 101 and the seat cushion 102 by the laterally outer and inner locking mechanisms 111, 112 is released.
That is, as shown in FIG. 9, if the front of a vehicle with the reclining seat 100 collides, the upper end portion of the laterally outer frame 103 is greatly tilted forward, but the laterally inner frame 104 is not particularly deformed. The reason is because the locked state between the laterally outer frame 103 and the cushion frame 110 by the laterally outer locking mechanism 111 is released.
That is, if the front of the vehicle running forward collides, the passenger is held in the reclining seat 100 by the seat belt 106 without being slipped out of the reclining seat 100, but a great load is applied to the seat belt 106 and also to the retractor 107 supporting an end of the seat belt 106. Because of this, the upper end portion of the laterally outer frame 103 is tilted forward.
If the upper end portion of the laterally outer frame 103 is tilted forward, the laterally outer locking mechanism 111 provided on the laterally outer frame 103 rotates in an anticlockwise direction in view from left side of the seat 100 indicated by an arrow A111 in FIG. 9. At this time, no deformation occurs in the laterally inner frame 104, so the laterally inner locking mechanism 112 does not rotate.
In addition, the laterally outer locking mechanism 111 and laterally inner locking mechanism 112 are constructed such that they allow the shaft 114 to rotate in the clockwise direction indicated by an arrow A114 in FIG. 9 but not to rotate in the opposite direction.
Therefore, even if the front of the vehicle collides and therefore the laterally outer locking mechanism 111 rotates in the anticlockwise direction, the shaft 114 will not rotate.
Because of this, if the front of the vehicle collides, and the laterally outer locking mechanism 111 rotates in the anticlockwise direction, relative rotation takes place between the laterally outer locking mechanism 111 and the shaft 114, even when the release lever 114 is not operated. As a result, the locked state between the laterally outer frame 103 and the shaft 114 by the laterally outer locking mechanism 111 is released. To solve such a problem, a technique has been proposed in Japanese patent laid-open publication No. 2004-290243 (hereinafter referred to as patent document 1). Note that in the following description of patent document 1, a reference numeral enclosed within brackets indicates a reference numeral employed in the drawings of patent document 1.
As shown in each FIG. 2-4, the technique of the patent document 1 aims to avoid rotate relatively between a rod (80) and a shaft (84a) even when the shaft (84a) connected with one seat back frame (12a) rotates as shown in FIG. 1 by such a manner that forming recesses (81) in the rod (80) and forming projections (85) in locking mechanisms (51a and 51b).
However, it is not prefer to form the recesses (81) in the rod (80) and form the projections (85) in the locking mechanisms (51a and 51b) as the technique of patent document 1 because the labor and cost of production must be increased due to high-precision process is required.
Further, in the technique of patent document 1, it is impossible to avoid relative rotation between the rod (80), which is a pipe, and the shafts (84a and 84b) beyond the length of recesses (81). Accordingly, when the shaft (84a) tries to move beyond the recesses (81), the rod (80) and the shafts (84a and 84b) rotate together. Consequently it is impossible to prevent the deformation of the seat back frame (12a) due to the unintentional releasing of locking mechanisms (51a and 51b) happens.